Disclaimer

This text is intended to give the public information about some elements of
the computer games Doom, Quake, and their sequels, by id Software. This text
was not written by id Software, so bugging them about its contents is probably
a very bad idea.

Additionally, the computer games referenced in the text are of an adult and
graphic nature. In no way is this text intended to promote violence of any
kind. Any references to violence in this text are meant in relation to the
playing of the computer game, not real violence. The author is adamantly
non-violent.

Additionally, this text is being presented in the form of a computer file.
Any illegal or damaging activity related to the use or transfer of this or
any other computer file is not the responsibility of the authors.

Trademark Information

All specific names included herein are trademarks and are so acknowledged: id
Software, DOOM, DOOM II, THE ULTIMATE DOOM, QUAKE, QUAKE 2. Any trademarks not
mentioned here are still hypothetically acknowledged.

Copyright Notice

This article is Copyright (c) 1998 by Tony Fabris. All rights reserved.

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the copies are exact and complete, the copies include the copyright notice in
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sort of a price or fee relating to any copies of this work in any form.

Well, I just got my reply from Bernd Kreimeier, so I think the last few
missing details about the BFG's behavior have finally fallen into place.

He was extremely helpful, and pointed out a couple places in the Doom
public code release that answered my questions. Specifically, we've now
got the exact time delay, damage, and range limitation information.
Thanks, Bernd!

And to add icing to the cake, Randy Pitchford and I have nailed down
the last few details about the Quake 2 BFG10K, so I've fleshed out that
section as well. Thanks, Randy!

This BFG FAQ has been a very unique project for me. Its development
cycle has spanned over two years, and it's been through many revisions.
Thanks to all the folks who e-mailed me about it, and the folks who
contributed.

I think my favorite part of this whole thing was seeing all the other
"Doom specific weapon" FAQ files appear on the net after the BFG FAQ
came out. All the way down to the "Pistol FAQ". The first one, I
recall, was originally intended as a joke... it was a "Rocket Launcher
FAQ" that started out as a satire of the BFG FAQ. It was hilarious,
and even had satires of the ASCII diagrams. Now these files are actual
legitimate FAQs in their own right.

When I first undertook this project, it was simply because I couldn't
get a straight answer to the question, "How does the BFG work" on
usenet. Now it's taken on a life of its own. With the Christmas
release of the Doom source code (Thanks, id!), I guess the whole
thing has come full circle.

It's been a fun ride!

Section 0 - Introduction

This FAQ file describes, in as much detail as possible, the behavior of the
BFG9000 weapon in the MS-DOS version of the games Doom, Doom II, and The
Ultimate Doom. It is not intended to answer general questions about the game
itself. Please refer to the other FAQ files for help in other areas of the
game. You can also frequent the rec.games.computer.doom.* newsgroups for more
information.

We began writing this FAQ out of necessity. We were frustrated at the apparent
inconsistencies in the way the weapon seemed to behave during game play,
especially during deathmatches. There were times when we would get killed by
the weapon when we thought we were completely safe. Conversely, there were
times when we thought we had used the weapon correctly against an opponent,
but they walked away unscathed.

Our intent is to provide players with enough information to attack effectively
with the BFG, and to correctly defend against it in a deathmatch. Our hope is
that this information will give players a new attitude toward the weapon. We
want to transform it from "The weapon we love to hate" into "The thinking
man's weapon".

With the 1997 release of both the Doom source code and the sources for the
Quake 2 game DLL, this FAQ will hopefully provide accurate information for
all versions of this unique weapon.

Initially, the information came from playtesting Doom. We would simply
theorize about the weapon's behavior and then test the theory on the network.

Testing was performed on Pentium computers running the MS-DOS versions of Doom II
and The Ultimate Doom. Tests were done both in single player mode and
in 4-player deathmatch mode. Testing was performed on the regular levels
as well as custom made levels. In some cases, a special .WAD
file was created to test situations that would be difficult to reproduce
with the regular levels.

At one point early in the development of the FAQ, we exchanged some
emails with American McGee at id Software. He filled in some very
important details for us-- for example, until American told us about
it, we didn't know that the game used a set of damage traces to
calculate blast area damage. His help was invaluable in putting
this FAQ together and getting it off the ground.

Recently, I was able to ask Bernd Kreimeier some specific questions
about the code. His answers, I hope, have cleared up any ambiguities
in the details.

Fairly accurate. Accurate enough to base your playing strategies on.
However, it has not been tested with every single version of Doom, and
there may be differences among platforms.

Then there's the issue of the Doom public code release. That code was
"cleaned up" by Bernd Kreimeier, who was given the sources by id
Software to prepare it for a public release. Bernd tells me that he
did not change the BFG code in the cleanup process, but the sources
are from a later date than the original commercial releases of Doom
and Doom 2. In his words:

It is the January 10th, 1997 version - a few TNT/Plutonia
mod's have been done in this code base, but I am in no
position to confirm whether this affected the BFG code.
I never looked at that part of the code, nor changed it.

Until I hear otherwise, I'm going to assume that the public code release
contains the same BFG behavior as the commercial releases. Everything
you see in this FAQ will be based on the old playtesting we did in 1995,
cross-referenced against the sources found in the 1997 public code
release.

Finally, now that the folks are modifying, compiling, and releasing
their own versions of Doom, who knows what they might change? The BFG
was an infamous feature in Doom, and will likely be the first target
for modifications. So read those README.TXT files before you play
a modified Doom.

Despite all of that, some items in this file may still be conjecture.
Please see section 5 if you suspect this FAQ contains
erroneous information.

The latest Doom-related FAQ files and other documents can be found at
all of the Doom mirror FTP sites. The central location for the Doom
mirrors is at ftp.cdrom.com. However, that site is usually quite busy,
and you may need to locate another mirror site from which to download.
Listing all the mirror sites is beyond the scope of this document.
See the 'DOOM: Rec.Games.Computer.Doom FAQ' or 'DOOM: FTP and WWW
Sites' postings in the rec.games.computer.doom.* newsgroups for a
complete list.

The URL of the directory that contains the Doom FAQ files (usually in
TXT format, compressed in a ZIP file) is:

The latest official version of the BFG FAQ is also posted monthly to
the rec.games.computer.doom.announce and .playing newsgroups. This is
part of the RGCD Periodic Information Postings (PIPs). If your news
server does not keep the articles long enough for you to find one of
the PIPs, they are archived at:

Section 1 - BFG Basics

The BFG9000 (or BFG) is arguably the most powerful weapon in the computer
games Doom, Doom II, and The Ultimate Doom. It is also the most difficult
weapon to use well in a deathmatch (multi-player competition), because it
does not behave in a simple 'point and shoot' fashion.

When you have it in your arsenal, the BFG is selected by pressing the 7
key on your keyboard.

When you pull the trigger, there is an excruciatingly long pause as the
weapon warms up. Then a large green ball of plasma is emitted from its
barrel. The plasma ball flies in the direction you fired it until it hits
a target or a wall. Like all weapons in Doom, it will fly straight through
decorative objects like torches or trees.

When the green ball hits a solid object, it detonates and does two types
of damage: Direct Hit and Blast Area.
Each damage type is outlined in its own section, later in the FAQ.

The general consensus is that BFG stands for Big Fragging Gun.
Well, that's the G-rated version at least. Hank Leukart's Official
Doom FAQ (the one that ships with the game) says so.

So is "Fragging" a deliberate softening of another famous F-word? Maybe.
But the term "frag" is an actual word, and it's used in Doom to represent
a confirmed kill in a deathmatch game. This comes from the idea that in
a deathmatch, you are killing your fellow space marines.
The definition of frag is:

frag Slang. Verb, transitive
fragged, fragging, frags
To wound or kill (a fellow soldier) by throwing
a grenade or similar explosive at the victim.

That's not to say that the the word Frag isn't often interchangeable
with the other word. And, of course, the Quake 2 manual calls the
new BFG10K the "Big, uh, freakin' gun."

Other good name suggestions that have found their way to the authors are
"Big Funny Gun" (Chris Somers) and the much more logical "Blast Field Gun"
(William D. Whitaker). I'm sure there are thousands of names you could invent
for it...

Listing all the locations that the BFG can be found is beyond the scope of
this document. For detailed information on the location of all weapons,
please consult the other FAQ files. Keep in mind
that the BFG appears more often in deathmatch games than it does in single
player games.

If you perform the above cheat correctly, but do not get the BFG, you may be
playing the shareware version of Doom. You must purchase the commercial
version of Doom from a retailer or id Software before the BFG can glorify
your screen.

The current version of the BFG is not the way id's designers
originally envisioned it. The BFG behaved quite differently in a
pre-beta release of Doom.

It worked by shooting multiple streams of different types of plasma
and fireballs. Because this required an unusually large number of
moving objects, it tended to slow down the game. Therefore, the BFG
was redesigned with the invisible blast area that is used today.

Recently, these early Doom versions have been distributed on the
internet. You can find screen shots and downloads at:

A direct hit with the BFG causes a random amount of damage between
100 and 800 points, in 100-point increments.

The base damage value for the green ball is 100 points, which gets
run through the missile damage randomization routine:

damage = ((P_Random()%8)+1)*tmthing->info->damage;

Note that the above code results in damage values in 100-point
increments, i.e., 600 or 700, but not 666.

A note about skill levels: Testing seems to show that weapons always
do the same amount of damage to monsters, but that the player objects
can absorb the weapons better at lower skill levels. Therefore, it
takes more shots to kill a player at lower skill levels, and fewer
shots at higher skill levels. This is why some players prefer to
deathmatch at the higher skill levels: The frags are quicker that way.

The Doom public code release bears this out. They perform a right
bitshift (a fast way to divide an integer by two) on the damage value
as follows::

And of course, armor is a factor as well. Depending on the type
and the amount of armor worn by a player, some armor will be
subtracted in lieu of health.

If your target is lucky enough to survive a direct hit, he is still
susceptible to damage from the blast area. This happens sometimes in a
deathmatch. Since there is a brief pause between the direct
hit and the blast area calculation, your victim may go through several
stages of fear and elation in the space of one second:

The direct hit is not limited by the same parameters as the blast area.
There is no range limit, and the damage does not decrease with distance.

The hard part is that the BFG's plasma ball travels at a fixed speed, and
can be avoided by an alert deathmatch player. The reference number for the
BFG ball's speed, as stored in the .EXE file, is 25. For comparison, rockets
travel at 20 and plasma gun shots travel at 25.

If it seems like this is too fast, and would not be easy to avoid, remember that
the plasma gun fires in a continuous stream. The BFG can only be fired once
every few seconds. The BFG's green ball is also very bright and large on the
screen. All of those factors make it generally easier to avoid in a deathmatch
game.

A direct hit in a deathmatch (against good players) is usually the result of
luck, or the result of a player that did not know the BFG ball was coming
towards him. See section 4 for details of a trick that can help you achieve
the latter scenario.

The direct hit can only damage one target. If there are two targets very close
together, the green ball can only hit one of them directly-whichever one it
touches first.

Section 3 - The Blast Area

After the green plasma ball detonates, and after the damage is calculated and
deducted from the target that received the direct hit (if any), the area effect
of the BFG is calculated. Targets that fall within a specially defined area
will take varying amounts of damage.

Simply put, the blast area is like an imaginary 'cone' or 'fan' of damage
traces that briefly extends outward from the attacking player. The cone always
points in the direction that the weapon was fired. For instance, if you
originally fired the weapon in the northwest direction, the cone will always
face northwest, regardless of which direction you're facing at the moment of
detonation.

Note that this does not mean that the attacker must continue to face in that
direction. The attacker is free to turn away from his targets, as long as he
moves to a position that keeps this imaginary cone pointed at them. Common
misconceptions are that you must be facing either the targets, the detonation
point, or the same direction as the weapon was fired. None of those things
are necessary in order to inflict damage.

Also note that this imaginary cone has no relation whatsoever to the
detonation point. The location of the detonation point is only important
for the direct hit (see section 2). Only the moment of detonation is
important, not the location. It is possible to have the green ball
detonate twenty miles away in a completely different room at a totally
different altitude, but the blast can still cause damage right next to
you.

The paragraphs above cover the basic concepts of the blast area. More
detailed information can be found in section 3D, below.

Since the Doom public code release, I'm revising this section.
Originally, we were told that there were 20 traces, each doing a
random amount of damage between 5 and 15 points. But now that I look
at the public code release, it's telling me a different story. I've
confirmed this with Bernd. The function "A_BFGSpray" is pretty simple,
and here's how it works:

There are 40 traces, and each one does 1-8 random points of damage in
a 16-iteration loop. Meaning each trace will do between 16 and 128
points of damage.

Because these traces radiate outward from the attacker in a fan shape, a
target will more likely be hit by a given trace if he is close to the
attacker. Therefore, targets closer to the attacker will generally take
more damage because they are hit by more traces.

If a target is very close to the attacker (for instance, standing right
next to him), the target might be within the hit range of all the traces.
The amount of blast area damage in this situation would be between 640 and
5120 points. However, all traces would not necessarily be absorbed by
that target, and might move on to other targets.
See section 3F, below, for more information on this
phenomenon.

A note about random numbers:

A phenomenon known as the 'bell curve' happens when you combine the
outcome of multiple random numbers. Players of book-and-paper role-playing
games may recognize it. In those games, you would often use
three dice to generate a random statistic. In theory, adding the three
dice would generate a random number between 3 and 18. But in reality,
the actual results would be weighted towards the middle of the range,
around eleven. The odds of getting a three or an eighteen are rare
because you'd have to roll 1+1+1 or 6+6+6. There's only one possible
combination for each outcome. On the other hand, rolling an eleven is
relatively easy: 6+4+1, 5+5+1, 3+3+5, etc. If you were to graph the
outcome of a thousand rolls, the graph would be shaped like an arc or
a bell, with more rolls coming up in the middle of the range of
possible values. Hence the name 'bell curve'. The role-playing games
use this to make certain random statistics more fair.

This applies to the damage traces, as well, because they are essentially
a group of multiple random numbers. For instance, although the possible
damage for a single trace is 16-128, the odds are that the total damage
from a trace will more likely be around 50-60 points, due to the bell
curve. The odds of doing full or minimum damage in that situation would
be extremely rare.

Actually, if you look at the Doom code, you'll find that even the
random numbers aren't random. They're "pseudo-random", and for a very
good reason: So that all four computers in a multiplayer game can be
synchronized. They pull the random numbers from a table whose index
changes each time it's accessed. Looking at the table, it's obvious
that there are no "runs" of all low or high numbers, so it's not
only unlikely that full or minimum damage would be done, it's
actually impossible in the current code.

The blast effect is instantaneous, but it does not activate until
the "S_BFGLAND4" frame plays. This can be seen in the source code
in the frame/action pointer table in "info.c".

What this means is that the "A_BFGSpray" function is triggered 16
game tics after the first death frame of the direct hit was
started. Assuming a game tic is 35 frames per second, then the
blast effect is calculated 0.4571428571429 seconds after the
detonation. Which, Captain, if I had any emotions, I'd be excited
about.

But what about the other thing?

Oh, you mean, when someone is running out from from behind a corner,
and it looks like the blast area should have missed them, but it got
them anyway? How can that be? They ran out from behind the corner
after the blast area was calculated!

Well, it's been a while (two years) since I LAN-playtested this
phenomenon. We were never able to nail it down under controlled
tests. The "A_BFGSpray" function calculates completely within a
single game tic, and if there's a slow computer in the game, all
of the computers will freeze until the slow computer is done with
its blast area calculations.

The only thing I can figure is, the guy's radius (which is larger
than his visible sprite) was within sight of the damage traces.
He took damage while he still seemed to be behind the corner, even
though he wasn't. More on this phenomenon below.

The blast area is a spread of invisible traces that radiate outward
from the attacking player. The damage for the traces is calculated shortly
after the green ball detonates against a target or a wall.

Here's the code for the function in the public code release. I've
waited two years to see this:

The traces radiate outward in an imaginary cone that is 90 degrees wide. This
is, coincidentally, about the same width as the player's field of view.

Because the code uses "mo->angle" as the source for its angle, the cone
always points the same direction that the green ball flew. For instance,
if you fire the green ball in the southeast direction, your cone of traces
will always radiate towards the southeast.

However, because it uses "mo->target" as the source for its attacks,
the traces radiate from where the player is standing, not from the
green ball.

So...

Regardless of how much you run and turn between the time you fire and the
time the green ball detonates, the traces will always radiate from your
location. Think of it like a tank with a gyroscopically stabilized turret:
only the cone's origin point moves around with you, not its direction.
The cone's direction remains fixed on the same compass heading.

From a technical point of view, the game engine does not actually keep track
of the cone while you're running around. That's just the effect it seems to
have. It simply uses the green ball's vector as the source angle for the
traces, and the player's current position as the source location.

Note that the vector of the green ball's flight is based on what direction
you were facing when the ball leaves the barrel of the gun, not when
you pulled the trigger.

Here's a diagram of how it works:

Note that this diagram is foreshortened. The detonation point would
have to be quite far away in order for the attacker to be able
to run that far. But the principle is the same, regardless of how far
the green ball flies: The damage cone is calculated after the green ball
detonates.

When the green ball detonates, the traces are calculated one at a time,
using the same criteria for calculation that the engine might use for a
bullet: If there is a solid object (a wall, etc.) between the target and
the attacker, the trace is harmlessly absorbed by the object. With one
exception: In order to hit a target with a bullet, you had to be facing
the target. You don't have to be facing your target in order to do damage
with one of the traces.

Quick review:

The cone of traces always points in the same compass direction, the
direction you originally fired the BFG.

You sort of 'carry the cone around' with you as long as the green ball
is still flying.

When the green ball detonates, the cone of traces does its damage
depending on where you're standing at that moment, and who is in the cone.

You do not have to be facing the targets to do damage, you only have
to maneuver into a position where the cone is pointing at your targets.

Revision time. It seems as though there is a hard limit on the
range. Bernd says he thinks this line:

P_AimLineAttack (mo->target, an, 16*64*FRACUNIT);

actually limits the traces to within 1024 (16*64) game units.
It's been a while since I playtested this, so I don't remember if
I was ever able to register a hit when outside of this range.

Whether it actually limits the range or not, outside that range
it would become increasingly hard to get a single trace to land
on a given target anyway. So just deathmatch under the assumption
that you can't hit anyone outside 1000 units.

If you are unfamiliar with the Doom engine's units, remember that a
standard teleporter pad is 64 units across. Line up 16 of those and
you've got a basic idea of what 1024 units is.

The blast damage is also limited to targets that have an unblocked line
of sight to the attacking player. This does not mean the attacker must
face the target. It means that the attacker must be in a position where
his traces can see the target, i.e., he could see the target if he were
facing in that direction.

The blast area can only hit as many targets as its traces can touch.
Originally, we stated that one trace can damage more than one target.
This was because we did tests where a single shot killed 25 imps. But that
was back when we thought there were only 20 traces. Now that we know
there's 40 traces, it seems as though the number of objects that can
possibly take damage is 40.

Of course, in regular game play, rarely are that many targets standing
in such a perfectly aligned pattern. Usually, some individual targets will
soak up more than one trace, while other traces miss targets completely.

The traces are calculated on a 'first come, first fragged' basis. For each
trace, the damage is calculated and subtracted from the target, and the
target dies if there's enough damage. Then the engine moves on to the
next trace.

Here is how it works:

(Please note: In the discussion below, we refer to 'line of sight' loosely.
Remember that the attacker does not need to be facing his targets to
inflict damage.)

In the following scenario, imagine that the attacker is standing in a direct
line with several targets (imps, perhaps) lined up in front of him, and the
green ball detonates on a wall somewhere:

The first couple of imps are close to the attacker. They crumble, having
soaked up some of the traces that are pointing ahead of the attacker. The
next few imps are a little further away, and absorb some more of the traces,
but not as many. They absorb fewer traces for two reasons:

because the imps in front of them absorbed some of them already, and

because they are further away and the traces are more spread out.

But they still die. The next imp gets damaged, but does not die. He has
soaked up the last trace that was headed in that general direction. The
last imp is not damaged at all because there are no more traces left in
his direction.

In order for the above scenario to work, the targets must be perfectly
aligned. For instance, in the following scenario, all of the targets take
full damage, because there's no one in front of them to soak up traces.

The one target in the back (Y) is still susceptible because it is not
blocked by another target. The attacker can see him through the gap. So, for
example, an imp standing directly behind a cyberdemon is fairly safe, but an
imp standing next to a cyberdemon is a sitting duck.

The moral to this story is: In deathmatch, do not depend upon other players
or monsters to absorb the BFG blast unless they are exactly between you and
your attacker. And you'd better hope they're very healthy. In all other cases
you take full damage.

Again, in the discussions that follow, we refer to 'line of sight' loosely.
You do not have to face your targets to hit them.

If a difference in altitude brings your target out of the sight of your
traces, then yes, it makes him safe from the blast damage. But if your
traces can see any part of him, he takes full damage regardless of how
much higher or lower you are than he is.

As far as altitude is concerned, the traces seem to use the same criteria as
your view does to determine if the target is visible. In other words, if both
you and the damage cone are facing the target, but the target is above the
top of the screen, you can't hit him.

But there is a catch. The upper and lower angle limit of the traces seems to
be the same as your view would be if your screen was fully zoomed in. For
instance, if you are displaying the status bar at the bottom of the screen,
your view window is slightly cut off at the top and bottom. Press the plus
(+) key repeatedly to zoom all the way in, and you can see what this means.
The BFG's traces seem to use the same angle as this full view does to
determine if they can hit the target. So if you've got the status bar
showing, you can actually hit someone who is off the top of your screen.
If you are fully zoomed in, your view seems to be an accurate representation
of the damage cone's angle.

Note: The angle limit of the traces is not affected by changing your
zoom level. The traces use the same angle regardless of what your zoom
is. It's just that zooming all the way in changes your screen's
aspect ratio. So you can see more stuff at the top and bottom of the
screen, stuff that normally would have been hidden behind the status
bar.

If you are standing on a ledge above your target, and you are so close
that you can 'touch' him (i.e., you can't step off the ledge because
you're bumping into him), your shots will go right over his head and
the blast damage will not affect him. This is because, technically, the
traces can't see him. Well, if you could look down you would see him,
but you can't look down in Doom. Must be those darned restrictive space
helmets.

No such luck. The only thing that reduces your damage is getting hit with
fewer traces. Here is how it works:

If you are hiding behind a decorative sprite (such as a tree or a technical
column) you are fully exposed. All weapons in Doom always pass completely
through decorative sprites.

If you are peeking over a podium, or partially obscured by a raising lift,
or a closing door, and only half or one-tenth of you is showing, you still
take the full amount of damage. The traces are calculated based on the
game's two-dimensional block map. As far as the game engine is concerned,
all of the traces can still hit you.

If you are hiding behind a vertical wall with your rear end peeking out,
I'm pretty sure you still take full damage because the traces auto-aim
at you. Tests seem to show that your distance from the attacker is more
important than how much of you is exposed.

Also remember that what counts as 'showing' may not be what you think. The
Doom engine uses the radius of the player to determine visibility. Your
player's aspect ratio does not change when you rotate. It also seems as
though your radius is slightly larger (in some cases) than the sprite
(picture) that represents your player. In tests, it is possible to inflict
damage upon a player that seems to be out of sight (no visible pixels) but
whose radius is large enough to count as 'visible' to the BFG traces.

The BFG's traces are still active, even if the attacking player is
dead. So if you fire the BFG, then get fragged, do not press the space
bar to respawn your marine right away. Wait until the green ball has
detonated before you respawn.

Here's why:

Even after being fragged, you can still see the action from your fixed
point of view on the ground (your 'dead' state). The traces remain
active and can still frag an opposing player (hopefully the one that
fragged you). The traces will radiate from your dead body's 'eyes'.
The traces still follow the same rules, i.e., they radiate in the
direction the green ball was fired, regardless of which direction your
'dead view' is facing.

In a previous version of this FAQ, we reported that you will lose
the chance to frag your opponent if you respawn before detonation.
Several people pointed out to the authors that the statement was in
error. The traces remain active even after respawning. Testing shows
that the traces do, in fact, continue to radiate from the dead body
even after you have respawned in a completely different area of the
map. This testing was performed at the prompting of Kirby Nixon, who
insisted that it was true. Whaddya know? He was right.

This means that, technically, you don't need to hang around and watch
your opponent in order for the traces to work. But Kirby pointed out
a good reason to wait for the detonation before respawning: Your dead
body's traces can frag you, too! Just because they were once your
traces doesn't mean you're immune. If you are unlucky enough to
respawn within your dead body's damage cone, you can kiss your butt
goodbye.

Of course, the same thing applies to projectile weapons like the
rockets and plasma. If you play enough deathmatch, you've
probably been fragged by your own rocket a few times. Don't be
embarrassed, it happens to the best of us...

Please note: Any projectile kills made by a respawned player (whether
by rockets, plasma, BFG traces, etc.) do not contribute to that
player's frag count. Killing yourself in this manner does not change
your frag count, either. This appears to be because the game engine
creates a new instance of the player-object at respawn-time, and
therefore 'forgets' to award that frag. In any case, if you wait
before respawning, you will get credit for the frag as long as you're
still dead. This is another reason to wait for detonation before
respawning. Special thanks to John Castelli for pointing this one out.

Each BFG shot is tracked and calculated independently. The game
engine's code is object-oriented, and has no trouble keeping track of
multiple blast areas. Each damage cone's direction is based on the
direction of its corresponding green ball.

The origin point of the damage cone is based on the current location
of the marine who fired it (even if that marine is just a dead body-
see section 3I for more info).

Section 4 - Deathmatch Techniques

Many deathmatch players moan and groan when the BFG is used successfully
against them. 'What a cheap frag, you craven coward!' they shout. Well,
they usually use fewer words to express the idea, but that's what they
mean. This is usually due to a lack of understanding about how the weapon
works.

The purpose of this FAQ is to educate players about how the BFG behaves.
If you know how it works, you will know how to defend yourself against it.
You will also know how to effectively attack with it. If both (or all four)
players have the same knowledge about how the weapon functions, then the
BFG by definition is not unfair. If you play against an opponent who does
not know how the BFG works, then you should make sure to educate them on
its behavior before turning them into paste.

Having said that, the following things are debatable regarding fairness.
I'm not saying they are patently unfair, I'm just saying that their fairness
is debatable:

'Camping on' or 'guarding' the BFG when you are playing deathmatch 2.0,
and picking it up again every time it reappears.

Having a BFG left over from a previous level when there is no BFG
available to the other players on the current level.

In the last two examples, four-player deathmatch tends to cancel out any
advantages to those techniques. The remaining three players usually
coordinate and attempt to bring down the king of the hill in these
situations.

This requires, of course, that you know where the cone of damage actually
is. That, in turn, requires that you know where your attacker is and in what
direction he fired the weapon. That, in turn, requires that you know the
weapon was even fired at all. Which, in turn, may be difficult against a
player who has mastered the Silent BFG trick (See section 4D).

It still helps if you are playing the game with a stereo sound card and
headphones. This allows you to hear how far away and in which direction
your opponents are. If you think in three dimensions, the sounds you hear
in the game will give you a great tactical advantage.

You must understand completely how the weapon works before any avoidance
technique would be meaningful. So if you skipped ahead to this section, go
back and read the gory details.

With all that said, here are a few ideas. These are just things to try,
not necessarily good things in all cases.

Run past the attacking player so that you end up behind him. This
assumes that he is still facing the same direction as his damage cone.
You will be completely safe if you're on the opposite side of his cone.
This can backfire if you're not careful. You could end up three feet from
him and inside his cone when the green ball detonates, and soak up some
rays. That SPF 60 sun block won't help, either.

If you think you're about 1000 units away from the attacker, and you
don't think he's running towards you too fast, you can try running away,
and hope that the traces will be too thinned out to damage you seriously.

You can duck behind a nearby wall or a solid column. If you can see
your attacker, simply move so the column is between you and him. Wait for
the blast to detonate and die down, then step out from the column and place
some ordnance in his face. This technique works well on Doom II's 'Circle
of Death' level (11).

If you are very close to him, you can attempt to frag him before his
shot gets off. When he pulls the trigger, there is a slight pause while
the weapon warms up where you can still stop him dead in his tracks.
There is nothing more exhilarating than hearing his BFG spinning up,
then the sound of his scream as your super shotgun removes his face.
Muahahahaha...

If you are involved in a turning, running, spinning melee in an open
area, keep it up. Learn how to circle-strafe (use a combination of mouse
and keyboard controls to turn, run, and strafe all at the same time). If
you keep your attacker running in circles, his cone of damage will hardly
ever be pointing at you. He will eventually run out of ammo, or you will
frag him with conventional firepower. This technique works well in the
main courtyard of Doom II's 'Citadel' level (19). In this kind of melee, it is
nearly impossible to keep track of the cone (for either you or your
attacker), so you are really taking a gamble that the turning fight will
be to your advantage. But the exhilaration of winning that kind of fight
is one of the best rushes you can get.

If you are well armed and very healthy, you can judge whether or not
you can survive a blast area hit at your current distance. Then take
advantage of the fact that he's trying to keep you in his sight. He's got
a moment or two where he must leave himself exposed while he tries to soak
you with his traces. Pepper him with rockets or plasma. Grit your teeth
and take the blast area hit, but keep on him. Just don't get too close.

Stephen "Blue" Heaslip says this in his Doom Deathmatch Strategy
Guide (referring to an earlier release of this FAQ): "A point about BFG
defense not covered in the BFG FAQ is the preemptive strike. The best BFG
defense in an AltDeath game is to repeatedly pick up the BFG so your
opponent can't. The best BFG defense in a deathmatch 1.0 game is to kill
your opponent before he gets it." Thanks, Blue. I never mentioned this
one in earlier versions of the FAQ because I thought it was obvious.
But you're right, of course. The best defense is a good offense.

Anything else that takes advantage of the particular quirks of the
weapon. Remember that you can use your knowledge of BFG attacking techniques
to your advantage, like the examples above.

This requires, of course, that you know where the cone of damage actually
is. So if you looked here first, go back and check out the rest of this FAQ
for details.

Anyway, here's some ideas. Not necessarily comprehensive:

The best universally accepted method is to shoot a wall or solid column
that is very close to you. In this situation, your cone of damage roughly
equals the visible targets on the screen. This is because you don't have
much time to move around before detonation. Your targets don't have much
time, either (You will notice that all of the 'defense' tips in this FAQ
assume having time to react). Because we already know two things:

The direct hit is difficult to achieve,

The location of the detonation does not matter,

there is no reason to try shooting the green ball at your targets. Your
goal is to get the green ball to detonate as quickly as possible after
you decide upon your targets. Just make sure you're facing your targets
when you fire. If you have to rotate away from the direction of fire in
order to see your targets, your cone of damage may not hit them.

The next best thing is to use the strafe feature heavily. Don't rotate,
just keep strafing and keep your targets in sight while you wait for the
detonation. This also keeps your cone of damage roughly lined up with your
view, allowing you to use your view as a reference. If your targets are
trying to run behind you to get behind your damage cone, running backwards
while strafing may also help.

Combine the two previous attack methods: Shoot a nearby wall, then
strafe toward your targets. This takes advantage of the pause that
happens after detonation. You have a few heartbeats before the traces
are calculated, so use this time to strafe your targets into view.
The best example would be at a 90 degree hallway intersection: Shoot
the wall at the corner, then strafe out into the hall. This is really
just a shortened version of the level one strafe trick, except you
don't have to wait for detonation.

"Everything I need to know, I learned at Top Gun." Avoid turning fights.
See the related item under the defense techniques, above.

"Keep your friends close, but keep your enemies closer." Really. The
closer you are, the more traces will hit their faces. Don't even bother
firing if your opponents are more than 1000 units away: you will either
miss, or do very little damage.

Don't be afraid to use it in close quarters. You might think the BFG
is designed for open-area use, but it actually works best when things get
cramped. The 'shoot the wall' trick really mulches 'em in a narrow hallway.

Keep it loaded, then use it liberally. Find lots of ammo for it. Use
a backpack to double your ammo capacity. Then shoot it off whenever you
get the urge. For instance, every time you enter a new room or open a door.

Set up pre-timed shots that take advantage of its long warm-up time.
Like this: pull the trigger, then open the door. Or pull the trigger,
then drop off the ledge into the room with your target.

Shoot the green ball at a very distant wall (such as outdoors or down
a long hallway), then run into the room where your target is. He may not
know you even fired, or he may think it already detonated. Either way, you
can just stand there. When the ball eventually detonates, your target will
simply see himself crumble to the ground, realizing too late that you were
standing still because you were keeping your traces on him. See section 4E
for an example of this.

Use 'combo' moves. Use the above 'distant wall' technique, but switch
to a conventional weapon as you run into the room. Your traces still work,
even if you have switched weapons. Blast 'em with both the BFG traces and
something else at the same time. Special thanks to Dan Christensen for this
suggestion.

Bait your prey. Use the above 'distant wall' technique, but switch to
the pistol and fire it while running into the room. They will hear your
pistol and attempt to get very close to frag you. If timed correctly, they
will be right in your face at detonation time. Splat city.

Defending yourself against the BFG pretty much depends on your ability to
know precisely when it is being used against you.

If you are fortunate enough to play deathmatch with a stereo sound card and
headphones, you know that sound cues are vital to playing well in deathmatch.
In many cases, the only way a potential victim knows the green ball is in
the air is by the distinctive sound the weapon makes when fired. The
headphones can give him directional cues as to its origin, and therefore
point the way towards a proper escape.

So if you wish to get the drop on someone, wouldn't it be great if you
could put a silencer on that weapon? Well you can. A limitation in Doom's
sound code allows you to silence the firing sound of the BFG. Regardless
of the 'Number of Sound FX to Mix' that you chose in Doom's setup program,
your character can actually only utter one sound at a time. This includes
all weapons firing. If you cause your character to grunt, i.e., you jump
off of a ledge or press the space bar on a blank wall, you have a brief
period while the grunting sound is being played in which you can pull the
trigger and no sound will be emitted from the weapon. Your grunt makes a
little noise, but it's relatively quiet and is sometimes ignored by your
opponents.

I've seen other information that tells me I've got it backwards:
That you're supposed to fire first, then grunt. I don't know
which is correct. Try both and use whichever one works for you.

While it works well in theory, in practice the trick is hard to perform.
It also may be a little unfair. As with all secrets, it definitely makes
the game unfair if you don't share this information with your opponents.

As of this writing, there seems to be a small handful of players on the
doom newsgroups who use this trick. The first person to submit this trick
to the author of this document was John Fedor.

Interesting anecdote: When reviewing a draft copy of this FAQ, American
McGee at id Software informed us that they have been using the Silent BFG
trick in their deathmatch games since day one.

The level one strafe trick is not a deathmatch technique per se, but it's
a demonstration of the BFG behavior that educates many folks on how the
BFG really works. The act of performing this trick tends to open one's
eyes to the amazing possibilities of the weapon. It also proves some
points made in this FAQ.

Doug Bora first pointed this demo out to our particular group. Credit
for the original version of this demo goes to John Ripley of the UK.
The full deathmatch demo file PETALK2.ZIP is the first example of this
specific action. Since that time, this has been repeated by many folks on the Doom
newsgroups.

(If the link above does not work, please consult the other FAQ files for
information on FTP sites that carry doom-related files. The author
won't be updating this particular link if it changes.)

How to do this:

Set up a deathmatch game with Doom II, starting on level one, no
monsters, deathmatch 2.0, ultra violence skill level.

Player one (Green) will most likely appear on the ledge with the
chainsaw, BFG, rocket launcher, and super shotgun. Tell him to move so
that he is within view of that first entrance room, standing on the
ledge where he can see down the brightly lit hallway from his perch
above the brown room. He can either stand up on the starting ledge, or
hop down into that first brown room. Either way, it will work. Tell
him to sit tight right there. He is frag bait for this demonstration.

Player two (whoever) will stroll into the brown room and pick up
the BFG behind the column. Wave to the nice guinea pig waiting patiently
for you. (Hi Phil. Hi Ralph.)

Player two strolls down the brightly lit hallway to the intersection
where he can see the other dark room, way down the long hallway. You can
just make out the plasma gun sitting on that podium in there.

While facing the plasma gun from the intersection in the bright
hallway, fire the BFG. When the shot actually leaves the barrel of the
gun and begins traveling toward the plasma gun, strafe quickly back
toward the intersection where you can see Greenie standing
in the first brown room.

If you reached that hallway intersection in time (before the green
ball detonated in the plasma gun room) you will be rewarded with seeing
the frag bait get fragged. Well, at least damaged. Maybe fragged.

One extra credit point to anyone who guessed that you don't have to
be facing Green Boy to kill him. You just have to make it to that
intersection in time. You could be turned completely away from him, he
will still be hit by the traces. You can prove this by running straight
to the intersection rather than strafing to it.

This demonstration proves the following:

You don't have to be anywhere near, or even facing the detonation
point to damage your targets. You only have to move to a position where
your cone of traces is on them.

The cone of traces always points the same direction regardless of
which direction you turn.

You do not have to face your targets in order to hit them.

You can fire the BFG in a totally different area than where you want
your targets to be damaged.

Players who perform this stunt successfully the first time are usually
amazed that it actually works. This is also a good practice for using
similar moves in real deathmatches.

You have to see the detonation point in order to inflict blast area
damage.

The location of the detonation point is a factor in the blast damage
area calculations.

Only the moment of detonation is important. The location of the detonation
point is not used. See number 2, above.

The location you were standing when you fired, or the location of
targets at firing time, is a factor.

Only the location where you are standing when the blast detonates is
important. The compass direction that you fired is important, but not
the location where you fired. The traces are only calculated at
detonation time. The game engine does not care where the targets
are until the traces are calculated.

Your BFG blast can frag someone behind you, but only if they are
close enough to touch you.

You can frag someone behind you if they fall anywhere within the cone
of traces. Sure they can be behind you, but they don't have to be
touching you. In order to frag someone behind you, you must rotate
away from the direction you fired, then maneuver so that your targets
are within the cone behind you.

Having said that, if the victim is standing right next to the attacker,
at 90 degrees perpendicular to the cone of damage, they will fall within
the cone if they are in front of the attacker's centerline. But if they
are truly behind the attacker's cone of damage (behind the centerline of
the attacker), they will walk away unscathed.

This seems to be due to the fact that the player's 'hittable' radius is
larger than the player's 'walk into' radius. When you walk up to a player
and bump into him, his 'hittable' area is overlapping into your area.

This is an easy mistake to make when looking at a deathmatch game, where
everyone is moving around each other so quickly that it's hard to keep
track of the location of the cone of damage. If you really think you
fragged someone behind you, it's probably because of one of two reasons:

They were actually next to you and slightly forward of your
centerline.

You rotated away from the direction of fire, and the victim
stepped into the cone of damage that still existed behind you.

Read the entire FAQ to be sure we did not cover your point in
another section. Check the 'Common Misconceptions' section, above, too.

If you have a theory about the BFG behavior, please test it
carefully before submitting it. If you can't reproduce the effect under
controlled conditions, you were probably witnessing a side effect of one
of its known behaviors. Or perhaps it happened in a deathmatch game, where
the action is so fast that you often can't keep track of what's going on.

If you think you have tested your theory thoroughly and are ready
to submit the theory as proven, please prepare a short, precise description
statement that details how to reproduce the effect during game play. Demo
recordings are not necessary.

Appendix A - Quake Mods

The ability to make user-created code modifications to the Quake engine
was one of Quake's most important features. These modifications, called
"patches" or "mods" number perhaps in the thousands. Some of the patch
authors decided that Quake deserved a BFG, too. Here's a short list
of some of the Quake BFG patches I've run across in my travels.

Since Quake's code is totally different than Doom's code, these BFG
remakes can't be precisely like the original BFG. Most of them get pretty
close in terms of "feel", though. The biggest difference is that they
all have a "Z" direction for their damage cone, i.e., they can be aimed
upwards.

Note that this list is not comprehensive and isn't necessarily up to
date.

Deathmatch Plus

URL: http://www.demonic.demon.co.uk/dmplus.html
(Update 8-15-99: This is now a dead link. You're on your own.)
Author: William Harris
Comments: This patch includes other interesting weapons such as the
Cluster Bomb. This patch was specifically designed for deathmatch play.

The BFG 9500

Doom 2 Total Conversion

URL: http://members.aol.com/imarvintpa/index.htm
(Update 8-15-99: This is now a dead link. You're on your own.)
Author: Andy Bay
Comments: A Total Conversion project for Quake, allowing you to play Doom 2 with the Quake
engine.

Your Path of Destruction

URL: http://www.planetquake.com/doom
Author: Curtis Moxley
Comments: A Doom Total Conversion project for Quake, including another original
piece of QuakeC code for the BFG.

DeathX

URL: http://omega.simplenet.com/omega/
(Update 8-15-99: This is now a dead link. You're on your own.)
Author: Luke Whiteside (WeAsL)
Comments: A set of QuakeC modifications for deathmatch play, with several new
weapons including a variation on the BFG.

Requiem

URL: http://www.planetquake.com/requiem
Author: Requiem
Comments: A Conversion for single player and multi player Quake, with
extra attention given to making a balanced set of weapons.
Includes the good-old BFG.

Randy and I have corresponded, and between his team's research and a few peeks
at the Quake 2 public code release, we've got the BFG10K's behavior
pretty much figured out. I'm only going to review it briefly here, and
you can go look at Randy's FAQ for all the details. So, in other words,
the torch has been passed.

Briefly, the main differences between the Quake 2 BFG and the Doom
BFG are:

If you detonate it against a wall or floor next to you, there's a
small rocket-style blast radius at the detonation point. It can
hurt you. This is to keep you from using your old Doom BFG tricks.
But it can also allow you to BFG jump, similar to rocket jumping.

The green ball shoots green lasers at targets as it flies along.

The direct hit is more powerful.

The area damage (called the "BFG Effect" in the source code) isn't
done with 40 damage traces. Instead, you must triangulate
lines-of-sight between the target, the detonation point, and the
attacker. In other words, to take damage, the target must be within
an imaginary line-of-sight to both the attacker and the ball.

The BFG Effect has a hard-coded 1000-unit range limit, similar to
Doom. But the range is measured from the detonation point instead
of from the attacker. (The way it should be!)

The BFG Effect damage amount is up to 500 points per target, with
an inverse square falloff between the detonation point and the
1000-unit limit. Here is the code line:

points = self->radius_dmg * (1.0 - sqrt(dist/self->dmg_radius));

So the farther away the target is from the detonation point, the
less damage the target will take.

In my experiences, the best way to attack with the BFG10K is similar
to the Doom way: Get a target in sight, then quickly detonate the
green ball on a wall, ceiling, or floor next to you. The only twist
is that you need to keep out of the way of the local blast radius.
You also need to make sure that the ball is detonated is a place
that's got a clear line-of-sight to the target. For example,
shooting the back side of a column, unlike Doom, is useless in
Quake 2.

The best way to defend against the BFG10K is to hide and/or run from
the ball. It keeps you out of the way of the lasers, as well as
keeping you out of the way of the BFG effect.

That's about all I need to say about the BFG10K (hey, that rhymes).
Check out Randy's FAQ for the rest. See you on the Quake 2 servers!
I'll be the one gathering cells for my BFG...